The present invention relates generally to temperature sensing apparatus, and more particularly to apparatus for determining the existence of normal temperature levels at a steam trap or other receptacle designed to be maintained at a substantially constant or normal temperature level. In its operation, the apparatus compares temperature levels and detects deviations that may occur at the detector location to the normal or desired temperature, whereby defective operation in a system, such as a steam system, is detectable. Steam trap usage is the normal and typical application for the apparatus of the present invention.
A typical steam trap is a pipe coupled automatic valve that permits condensed steam (condensate) to pass but which acts as a barrier to noncondensed steam. Thus, steam trap failure may occur with either the steam trap while in the open position, the closed, or partially open position. System efficiency is sacrificed upon the occurrence of failures in the steam trap or other steam consuming apparatus. In particular, a closed failure normally results where the steam trap mechanically fails or becomes clogged or plugged with dirt, scale or other residue, thus reducing heat transfer efficiency as well as the possible generation of carbonic acid, an acid which may cause corrosion in the steam system. An open failure, on the other hand, results in tremendous energy waste, undesired pressurization and an excessively high temperature in condensate systems with resultant inefficiency of the steam system.
In any failure mode, the defective steam trap can be detected through the monitoring of the localized temperatures at certain predetermined locations during system operation. Such failures, therefore, can be detected by means of appropriate temperature sensing apparatus operative in the ranges of the steam system being monitored. In particular, failures are detectable by means of monitoring the temperature levels occurring adjacent the steam trap inlet and outlet during normal operation and wherein temperature changes are indicative of either a failing or already failed steam trap which is designed or adapted to operate at a unique, relatively constant temperature level.
Heretofore, a number of apparatus and methods have been employed for detecting such failures. These include the use of contact stethoscope devices, chemical sensors which undergo visual changes, the intermittent opening or venting to atmosphere of valves in steam discharge lines for direct visual inspection, the use of pyrometric measuring devices, infrared emission detecting devices, pressure gauges and surface thermometers. These are standard systems which are in wide usage today. Depending upon which sensing apparatus is employed, however, a varying amount of benefit is obtained and normally at varying costs. Thus, while infrared emission sensors or detectors are desirable, they are extremely expensive. Listening and visual detection devices also offer benefits, however they, too, are rather expensive and/or subject to erroneous interpretation. Pyrometric and pipe surface thermometer measurements, on the other hand, offer similar modes for detecting temperature (i.e. surface temperature measurement) although at somewhat lesser cost.
The present invention provides permanent, continuous monitoring of temperature for convenient comparison of deviations to the pre-set zero datum point representative of a unique or normal temperature level.
Accordingly, the present invention is directed to a low cost, reliable temperature detecting apparatus which compares or detects deviations from unique or normal temperature levels and which can be employed in conjunction with the typically encountered rounded or curved pipe surfaces present in the lines used in virtually all steam systems. Furthermore, due to its low cost, the present invention may be more advantageously employed at a variety of locations in such systems for providing continuous monitoring in the severe environments normally encountered in steam systems. Further, because of its construction, the steam trap failure detector of the present invention is both reliable, and with its reliability being achieved at modest cost levels, particularly relative to the value to the user of the information obtained and the long and useful life of the apparatus. Thus significant advantages are available for most normal steam systems.
The above recited objects and advantages of the present invention as well as various others will, however, become more apparent upon reference to the following description of the present invention with respect to the following drawings. Although it is recognized that the present invention is described with respect to its presently preferred embodiment, various modifications, including those referred to hereinafter, may be made without departing from the spirit and scope of the present invention.